Scanning conversion apparatus and method

ABSTRACT

In the scanning conversion apparatus, a first converter converts input interlaced scan data into progressive scan data, and a second converter converting the progressive scan data output from the first converter to interlaced scan data.

BACKGROUND OF THE INVENTION

[0001] Various types of display apparatuses (e.g., televisions, computermonitors, etc.) typically use one of two types of displaymethods—interlaced scan and progressive scan. In both methods, imagesare divided into several scanning lines. In the interlaced scan method,the odd numbered scanning lines and the even numbered scanning lines arealternatively displayed. The odd numbered scanning lines of the imageare referred to as the odd field or top field. The even numberedscanning lines of the image are referred to as the even field or thebottom field. The top and bottom fields are alternatively displayed at ahigh speed such that a person sees a single composite screen. In theprogressive scan method, the image is displayed line by line; namely,all the scanning lines are displayed.

[0002] Interlaced scan data may be field based or frame based. Thefollowing is an example of frame based interlaced scan data, where “T”represents a top field, “B” represents a bottom field and “t” representstime:

[0003] T_(t), B_(t), T_(t+1), B_(t+1), T_(t+2) B_(t+2), . . .

[0004] As shown above, the frame based interlaced scan data includes atop field and a bottom field of an image derived at the same point intime. If the top and bottom fields from the same point in time werecombined, then a frame of progressive scan data would be produced. Next,the following is an example of field based interlaced scan data:

[0005] T_(t), B_(t+1), T_(t+2,) B_(t+3), . . .

[0006] In contrast to frame based interlaced scan data, field basedinterlaced scan data does not include top and bottom fields from thesame point in time. Combining top and bottom fields of field basedinterlaced scan data to create a frame of progressive scan data mayresult in a poor image, particularly when a large amount of motion inthe images is present.

[0007] Different video generation devices (e.g., computers, DVD players,video tape players, etc.) typically generate video data according to oneof the interlaced scan or progressive scan method. As such, the videogeneration device may not produce video data according to a methodcompatible with the scan method expected by a desired display device.

SUMMARY OF THE INVENTION

[0008] The present invention provides a scanning conversion apparatusand method that allows conversion of progressive scan data intointerlaced scan data, conversion of interlaced scan data intoprogressive data, or both.

[0009] For example, in one embodiment, a first converter converts inputinterlaced scan data into progressive scan data, and a second converterconverts the progressive scan data output from the first converter tointerlaced scan data. In one exemplary embodiment, theinterlaced-to-progressive converter and the progressive-to-interlacedconverter are connected in series to generate interlaced scan datasynchronized with progressive scan data output by theinterlaced-to-progressive converter.

[0010] In an exemplary embodiment of converting interlaced scan datainto progressive scan data, one of a number of different conversiontechniques is selected to perform the conversion. The selection is basedon the interlaced scan data being converted.

[0011] For example, in one embodiment, the conversion techniques includea spatial interpolation technique, a weave technique and aspatial/temporal interpolation technique. The spatial interpolationtechnique involves performing spatial interpolation on a current fieldof the input interlaced scan data to produce a field of complementaryscan data that together with the current field represents a frame ofprogressive scan data. The weave technique involves alternatelyoutputting two consecutive fields of the interlaced scan data on a scanline by scan line basis to produce a frame of progressive scan data. Thespatial/temporal interpolation technique involves performingdirectionally adaptive spatial interpolation using the current field, atleast one previous field and at least one subsequent field of the inputinterlaced scan data to produce a field of complementary scan data thattogether with the current field represents a frame of progressive scandata.

[0012] The spatial interpolation technique is selected when a currentfield of the input interlaced scan data is one of preceded and followedby a field of a same type. The weave technique is selected when theinput interlaced scan data is frame based interlaced scan data. Thespatial/temporal interpolation conversion technique is selected when theinput interlaced scan data is field based interlaced scan data.

[0013] In an exemplary embodiment of the interlaced-to-progressiveconverter, a conversion structure is configured to generate differentstreams of scan data from input interlaced scan data, the differentstreams of scan data representing conversion of the input interlacedscan data into progressive scan data according to one of the abovedescribed techniques. A selector is configured to selectively output thedifferent streams of scan data as progressive scan data.

[0014] For example, the conversion structure includes an interpolatorconfigured to interpolate lines of a frame of progressive scan datamissing from a current field of the input interlaced scan data byspatially interpolating the missing lines using the current field. As afurther example, the conversion structure is configured to supply theselector with the input interlaced scan data of a current field and oneof a preceding and following field of the input interlaced scan data. Asa still further example, the conversion structure includes aspatial/temporal interpolator configured to perform a spatial/temporalinterpolation conversion technique on the input interlaced scan data toproduce a portion of the progressive scan data.

[0015] In this example, the selector is configured to select output fromthe interpolator as a portion of the progressive scan data when thecurrent field of the input interlaced scan data is one of preceded andfollowed by a field of a same type. The selector is also configured toselect data from the current field of the input interlaced scan data anddata from one of a previous or next field of the input interlaced scandata as the progressive scan data when the input interlaced scan data isframe based interlaced scan data. The selector is further configured toselect output from the spatial/temporal interpolator as a portion of theprogressive scan data when the input interlaced scan data is field basedinterlaced scan data.

[0016] In another exemplary embodiment, the converter structure includesa spatial interpolator and a temporal interpolator. The spatialinterpolator is configured to perform spatial interpolation of a currentfield of interlaced scan data along a single direction to produce afirst complementary field in a first mode indicated by a controlcommand, and is configured to perform directionally adaptive spatialinterpolation of the current field to produce a second complementaryfield in a second mode indicated by the control command. The temporalinterpolator is configured to perform temporal interpolation using thecurrent field of interlaced scan data, at least one previous field ofinterlaced scan data and at least one subsequent field of interlacedscan data to produce a third complementary field in at least the secondmode indicated by the control command. The converter structure furtherincludes a conversion mode output device receiving output of the spatialinterpolator and the temporal interpolator and generating a frame ofprogressive scan data based on the control command.

[0017] For example, the conversion mode output device is configured tooutput the current field and the first complementary field on a scanline by scan line basis to produce a frame of progressive scan data inthe first mode indicated by the control command; and is configured tocombine the second complementary field and the third complementary fieldinto a composite complementary field and to output the current field andthe composite complementary field on a scan line by scan line bases toproduce a frame of progressive scan data in the second mode indicated bythe control command. In yet a third mode, the spatial interpolator isconfigured to output the current, the temporal interpolator isconfigured to output one of the previous field and next field, and theconversion mode output device is configured to alternatively output theoutput from the spatial and temporal interpolators on a line by linebasis.

[0018] In an exemplary embodiment of the progressive-to-interlacedconverter, a counter generates count values at a progressive scanningfrequency such that the count values are associated with a period of theprogressive scan data. A write address generator generates writeaddresses for writing progressive scan data into a memory based onoutput of the counter, and a read address generator generates readaddresses for outputting the progressive scan data written into thememory as interlaced scan data. In one exemplary embodiment, an addresscontroller selectively applying the write and read addresses to thememory from the write and read address generators.

[0019] In one exemplary embodiment, the counter generates count valuesassociated with different periods of the progressive scan data based onwhether the progressive scan data is being converted into one of an oddand an even field of interlaced scan data.

[0020] In another exemplary embodiment, the write address generatorincludes a first write address generator generating first writeaddresses associated with a first of two consecutive scan lines ofprogressive data based on the count values and a second write addressgenerator generating second write addresses associated with a second ofthe two consecutive scan lines of progressive scan data based on thecount values. Here, a write address controller selectively outputs oneof the first and second write addresses based on whether the progressivescan data is being converted into one of an odd and even scan line ofinterlaced scan data.

[0021] In a still further example of a progressive-to-interlaced scandata converter, the converter includes a timer indicating a timing oftwo consecutive scan line of progressive scan data. Here, a writeaddress generator receives a control signal indicating which of the twoconsecutive scanning lines to write into a memory, and the write addressgenerator generates write address for the indicated scanning line basedon the timing indicated by the timer. Also, a read address generatorgenerates read addresses to read the written line from the memory, andthe read address generator begins the generation of the read addressesbased on the timing indicated by the timer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will become more fully understood from thedetailed description given below and the accompanying drawings, whereinlike elements are represented by like reference numerals, which aregiven by way of illustration only and thus are not a limit on thepresent invention and wherein:

[0023]FIG. 1 illustrates a scanning conversion apparatus according toone example embodiment of the present invention;

[0024]FIG. 2 illustrates a relationship between the original interlacedscan data IDATA and the generated progressive scan data PDATA in FIG. 1;

[0025]FIG. 3 illustrates an example embodiment of theinterlaced-to-progressive converter (IPC) in FIG. 1;

[0026]FIG. 4A illustrates an example of spatial interpolation;

[0027]FIG. 4B illustrates an example of a block (i,j) of pixels;

[0028]FIG. 4C illustrates an example of neighboring blocks for the block(i,j);

[0029]FIG. 4D illustrates vertical low-pass filtering performed toremove vertical noise;

[0030]FIG. 4E illustrates the correlations of 7 directions;

[0031]FIG. 4F provides an illustration to explain the calculation ofvertical edge;

[0032]FIG. 5 illustrates another example embodiment of the IPC in FIG.1;

[0033]FIG. 6 illustrates an example embodiment of theprogressive-to-interlaced converter (PIC) of FIG. 1;

[0034]FIG. 7 illustrates waveforms input by and output by elements ofthe PIC in FIG. 6;

[0035]FIG. 8 illustrates another example embodiment of theprogressive-to-interlaced converter (PIC) of FIG. 1; and

[0036]FIG. 9 illustrates waveforms input by and output by elements ofthe PIC in FIG. 8.

DETAILED DESCRIPTION OF EMBODIMENTS

[0037] Scanning Conversion Apparatus

[0038]FIG. 1 illustrates a scanning conversion apparatus according toone example embodiment of the present invention. As shown, aninterlaced-to-progressive converter (IPC) 210 receives interlaced scandata IDATA such as generated by a video generating device (e.g., a videotape player, DVD player, etc.), and converts the interlaced scan dataIDATA to progressive scan data PDATA. The generated progressive scandata PDATA may form one output of the scanning conversion apparatus. Aprogressive-to-interlaced converter (PIC) 220 receives the generatedprogressive scan data PDATA, and converts the generated progressive scandata PDATA to interlaced scan data IDATA′. The generated interlaced scandata IDATA′ may form an output of the scanning conversion apparatus. Aswill be discussed in detail below, because the generated interlaced scandata IDATA′ is generated from the generated progressive scan data PDATA,a better synchronization exists between the generated progressive scandata PDATA and the generated interlaced scan data IDATA′ than existsbetween the original interlaced scan data IDATA and the generatedprogressive scan data PDATA.

[0039]FIG. 2 illustrates a relationship between the original interlacedscan data IDATA and the generated progressive scan data PDATA that willbe used below in the detailed descriptions of the example embodiments ofthe IPC 210. FIG. 2 shows a current field X of the interlaced scan dataIDATA that includes scan lines (i−1), (i+1), etc. with respect to areference scan line (i), a previous field X−1 that includes scan lines(i−2), (i), and (i+2), and next field X+1 that includes scan lines(i−2), (i), and (i+2). As further shown, after conversion by the IPC210, a frame of progressive scan data having scanning lines (i−2)′,(i−1)′, (i)′, etc is created. The relationship between the scanninglines of the interlaced scan, fields and the progressive scan frameswill be described in greater detail below in explaining the operation ofthe IPC 210.

[0040] IPC of the Scanning Conversion Apparatus

[0041]FIG. 3 illustrates an example embodiment of theinterlaced-to-progressive converter (IPC) in FIG. 1. As shown, the IPC210 includes first, second and third memories 2, 4 and 6. The firstmemory 2 stores at least successive lines of a current field of theinterlaced scan data IDATA. For example, using the relationshipestablished in FIG. 2, the first memory 2 stores at least the (i−1)thand (i+1)th scan lines, respectively, from field X. The second and thirdmemories 4 and 6 store at least a scan line, lying between theconsecutive scan lines stored in first memory 2, for the previous fieldand next field, respectively. For example, using the relationshipestablished in FIG. 2, the second and third memories 4 and 6 store atleast the ith scan line from field X−1 and ith scan line from field X+1,respectively. The number of scan lines stored by the first, second andthird memories 2, 4 and 6 will become more apparent from the detaileddiscussion below.

[0042] An interpolator 10 uses two consecutive scan lines stored in thefirst memory 2 to generate an interpolated scan line. The interpolationperformed by the interpolator 10, in one embodiment, is spatialinterpolation. Using the relationship established in FIG. 2, a simplespatial interpolation will be described with reference to FIG. 4A. FIG.4A illustrates a pixel P(n, i−1, X), where n represents the position inthe scanning line, i−1 is the scanning line on which the pixel lies andX is the field including the pixel. FIG. 4A further illustrates acorresponding pixel P(n, i+1, X) along a direction dirO in the nextscanning line i+1 of field X. As shown the direction dirO isperpendicular to the scanning lines. A pixel P(n, i′) that would lie onthe scanning line (i)′ in the direction dirO if the scan data whereprogressive scan data is interpolated by averaging the pixels P(n, i−1,X) and P(n, i+2, X). For example, P(n, i′)=(P(n, i−1, X)+P(n, i+1,X))/2.

[0043] Motion Adaptive Converter

[0044] A motion adaptive converter 12 also receives the scanning linesstored by the first memory 2, and further receives the scanning linesstored by the second and third memories 4 and 6. The motion adaptiveconverter 12 analyzes the amount of motion present in the imagesrepresented by the interlaced scan data, and generates pixel data for aprogressive scan line based on this analysis. This process will now bedescribed in detail below.

[0045] In the following discussion of the motion adaptive converter 12,x_(k) ^(n)(i,j) means the k_(th) pixel value in a block (i,j) of then_(th) field. And, x^(n)(i,j) means the (i,j) pixel value of the n_(th)field. FIG. 4B illustrates an example of a block (i, j).

[0046] The motion adaptive converter 12 calculates the SAD (sum ofabsolute difference) for “motion detection” between a previous fieldx_(k) ^(n−1)(i, j) and next field x_(k) ^(n+1)(i, j) in block-wisemanner as shown in FIG. 4B and equations (1) and (2) below.$\begin{matrix}{{{sad}( {i,j} )} =  {\frac{1}{8} \cdot \sum\limits_{k = 0}^{7}} \middle| {{x_{k}^{n + 1}( {i,j} )} - {x_{k}^{n - 1}( {i,j} )}} |} & (1) \\{{{SAD}( {i,j} )} = {\frac{1}{4} \cdot {\sum\limits_{m = {i - 2}}^{i + 1}{{sad}( {m,j} )}}}} & (2)\end{matrix}$

[0047] where N_(L)=pic_height, and $N_{B} = {\frac{pic\_ width}{8}.}$

[0048] The motion adaptive converter 12 determines a motion detectionthreshold from the following criterion in equation (3).

TH _(M)(i j)=(STD _(m)(i,j)<T _(M1))?T _(M1):(STD _(m)(i,j)>T _(M2))?T_(M2) :STD _(m)(i,j)  (3)

[0049] where T_(M1) and T_(M2) are design constraints set by thedesigner through empirical study (e.g., T_(M1) may be set to 8 andT_(M2) may be set to 16), and where STD_(m)(i, j) is a so-called“modified for simplification” standard deviation of the 4×8 pixelssurrounding the pixel of interest within 2 upper blocks and 2 lowerblocks of the current field X according to FIG. 4B and equation (4)below. $\begin{matrix}{{{STD}_{m}( {i,j} )} =  {\frac{1}{32} \cdot {\sum\limits_{{m = {i \pm 1}},{i \pm 3}}^{\quad}\sum\limits_{p = 0}^{7}}} \middle| {( {\frac{1}{32} \cdot {\sum\limits_{{l = {i \pm 1}},{i \pm 3}}^{\quad}{\sum\limits_{k = 0}^{7}{x_{k}^{n}( {l,j} )}}}} ) - {x_{p}^{n}( {m,j} )}} |} & (4)\end{matrix}$

[0050] If SAD(i,j)≧TH_(M)(i, j) then the pixel of interest has globalmotion and a “motion judder” value m_(J)(i,j)=1; if not m_(J)(i,j)=0.

[0051] Next, the motion adaptive converter 12 derives spatio-temporalinterpolation variables as defined by equations (5)-(14) below.

S ⁻¹(i, j)=x ^(n)(i−1,j−1)+2·x ^(n)(i−1,j)+x ^(n)(i−1,j+1)  (5)

S ₊₁(i,j)=x _(n)(i+1,j−1)+2·x ^(n)(i+1,j)+x ^(n)(i+1,j+1)  (6)

S(i,j)=|S ⁻¹(i,j)−S ₊₁(i,j)|  (7)

[0052] $\begin{matrix}{{\alpha_{I}( {i,j} )} = \{ \begin{matrix}0 & {{S( {i,j} )} > T_{I2}} \\1 & {{S( {i,j} )} < T_{I1}} \\\frac{T_{I2} - {S( {i,j} )}}{T_{I2} - T_{l1}} & {otherwise}\end{matrix} } & (8)\end{matrix}$

 m _(n)(i,j)=|x ^(n+1)(i,j)−x ^(n−1)(i,j)|  (9)

[0053] $\begin{matrix}{{m_{b}( {i,j} )} = | {{x^{n - 1}( {i,j} )} - \frac{{x^{n}( {{i + 1},j} )} + {x^{n}( {{i - 1},j} )}}{2}} |} & (10) \\{{m_{c}( {i,j} )} = | {{x^{n + 1}( {i,j} )} - \frac{{x^{n}( {{i + 1},j} )} + {x^{n}( {{i - 1},j} )}}{2}} |} & (11)\end{matrix}$

 M ₁(i,j)=max(m _(n)(i,j),α₁·max(m _(b)(i,j),m _(c)(i,j)))  (12)

M _(s)(i,j)=max(M ₁(i,j),M ₁(i−2,j),M ₁(i+2,j),M ₁(i,j−1),M₁(i,j+1))  (13)

[0054] $\begin{matrix}{{\alpha_{S}( {i,j} )} = \{ \begin{matrix}0 & {{M_{S}( {i,j} )} < T_{S1}} \\1 & {{M_{S}( {i,j} )} > T_{S2}} \\\frac{{M_{S}( {i,j} )} - T_{S1}}{T_{S2} - T_{S1}} & {otherwise}\end{matrix} } & (14)\end{matrix}$

[0055] With respect to the above variables, T_(I1),T_(I2), T_(S1) andT_(S2) are design constraints set by the system designer based onempirical study. For example, T_(I2) may be set to 50, T_(I2) may be setto 306, T_(S1) may be set to 19 and T_(S2) may be set to 18. Thevariable S(i,j) represents the complexity of the image at block (i,j). Arelatively larger value of S(i,j) indicates a more complex image, and arelatively smaller value of S(i,j) indicates a less complex image.M₁(i,j) is 4-bit quantized value and 0≦M₁(i,j)≦31 (value greater than 31is clipped to 31).

[0056] The final spatio-temporal interpolation pixel value Y_(ST)(i,j)is soft-decided by a weighted average of Y_(S)(i,j) and Y_(T)(i,j).

Y _(ST)(i,j)=Y _(S)(i,j)×α_(S)(i,j)+Y _(T)(i,j)×(1−α_(S)(i,j))  (15)

[0057] where Y_(S)(i,j) is a directional interpolation pixel valuederived as discussed in detail below and Y_(T) (i,j) is atemporally-calculated pixel value${Y_{T}( {i,j} )} = {\frac{1}{2} \cdot {( {{x^{n + 1}( {i,j} )} + {x^{n - 1}( {i,j} )}} ).}}$

[0058] The motion adaptive converter 12 performs one of aspatio-temporal interpolation Y_(ST) and temporal interpolation Y_(T)based on the amount of motion in the image. If there is little or nomotion, the temporal interpolation is applied. If not, spatio-temporalinterpolation is applied.

[0059] More specifically, if one or more than one of the neighboringmotion judders m_(j) (i,j) is “1” then spatio-temporal interpolationY_(ST)(i,j) is applied. If none of the neighboring motion juddersm_(J)(i,j) is “1”, then temporal interpolation Y_(T)(i,j) is applied.The shaded blocks in FIG. 4C surrounding the block (i,j) containing thepixel of interest represent one possible example of neighboring blocks.Hence the motion judders of these neighboring blocks are considered theneighboring motion judders.

[0060] Next, the generation of the directional interpolation pixel valuewill be discussed in detail. First, vertical low-pass filteringg_(n)(i,j) is performed to remove vertical noise as shown in FIG. 4D andexpression (16). $\begin{matrix}{{g_{n}( {i,j} )} = \frac{{x_{n}( {{i - 2},j} )} + {6 \times {x_{n}( {i,j} )}} + {x_{n}( {{i + 2},j} )}}{8}} & (16)\end{matrix}$

[0061] The correlations of 7 directions are calculated by weighted SAD(sum of absolute difference) with weight (1,1,2,1,1) on the filtereddata as illustrated in FIG. 4E, and each SAD is denoted byWSAD_(dir)(i,j) with dir=0,±1±2,±3.

[0062] Then, the global and local optimal directions are given asfollows. $\begin{matrix}{{DIR}_{GLOBAL} = {\underset{dir}{ARG}( {\min\limits_{3 \leq {dir} \leq {+ 3}}( {W_{dir} \times {WSAD}_{dir}} )} )}} & (17) \\{{{DIR}_{LOCAL} = {\underset{dir}{ARG}( {\min\limits_{1 \leq {dir} \leq {+ 1}}( {W_{dir} \times {WSAD}_{dir}} )} )}}{where}} & (18)\end{matrix}$

[0063] where $\begin{matrix}{W_{dir} = \{ \begin{matrix}1.0 & {{dir} = 0} \\1.25 & {{dir} = {\pm 1}} \\1.375 & {{dir} = {\pm 2}} \\1.5 & {{dir} = {\pm 3}}\end{matrix} } & (19)\end{matrix}$

[0064] Reliability improvements on DIR_(GLOBAL) and DIR_(LOCAL) areobtained according to expressions (20) and (21) below.

If |W _(DIR) _(GLOBAL) ·WSAD _(DIR) _(GLOBAL) −W _(DIR) _(LOCAL) ·WSAD_(DIR) _(LOCAL) |<150, Let DIR_(GLOBAL)=DIR_(LOCAL)  (20)

If ((W _(DIR=1) ·WSAD _(DIR=1) ≦W _(DIR=0) ·WSAD _(DIR=0))&(W _(DIR→−1)·WSAD _(DIR→−1) ≦W _(DIR=0) ·WSAD _(DIR=0))), LetDIR_(GLOBAL)=DIR_(LOCAL)=0  (21)

[0065] Denoting the interpolated pixel value in DIR_(GLOBAL) asdirection “A” and the upper/lower pixel values in DIR_(LOCAL) asdirections “B” and “C”, respectively, the motion adaptive converter 12determines the directionally interpolated pixel value Y_(DIR) _(—)_(OPT) as:

Y _(DIR) _(—) _(OPT)=median(A,B,C)  (22)

[0066] In order to preserve the vertical edge of the image, ameasurement of vertical edge “D” is calculated as shown in FIG. 4F andexpression (23) below. $\begin{matrix}{D = {\sum\limits_{k = 0}^{7}\quad d_{k}}} & (23)\end{matrix}$

[0067] The edge orientation adaptive spatial interpolation pixel valueY_(S) is obtained by the weighted average of Y_(DIR) _(—) _(OPT and Y)_(DIR0), which means the soft-decision of the pixel value with optimaldirection and the pixel value with vertical direction is then determinedby the motion adaptive converter 12, according to expression (24) below.

Y _(S)=α_(D) ×Y _(DIR0)+(1−α)×Y _(DIR) _(—) _(OPT)  (24)

[0068] where $\begin{matrix}{\alpha_{D} = \{ \begin{matrix}0 & {D < T_{1}} \\1 & {D > T_{2}} \\\frac{D - T_{1}}{T_{2} - T_{1}} & {otherwise}\end{matrix} } & (25)\end{matrix}$

[0069] Here, T₁ and T₂ are design constraints set by the designer basedon empirical study. For example, T₁ may be set as 434 and T₂ may be setas 466.

[0070] IPC Continued

[0071] This completes the detailed description of the motion adaptiveconverter 12. Returning to FIG. 3, the detailed description of the IPC210 will now be completed. As shown, a multiplexer 14 receives the scanlines from the first memory 2, receives the output of the interpolator10 and receives the output of the motion adaptive converter 12. Acontroller 16 controls the multiplexer 14 to selectively output one ofthe received inputs. The controller 16 also controls the operation ofthe motion adaptive converter 12.

[0072] The controller 16 controls the multiplexer 14 and the motionadaptive converter 12 based on received video information. The videoinformation is header information taken from the video stream beingreceived by the scanning conversion apparatus. As is well known, thisvideo information will indicate whether a field of interlaced scan dataIDATA is a first field in the video stream, is a top field or a bottomfield, and is frame based or field based interlaced scan data. Thecontroller 16 receives this video information for the current field X,the next field X+1 and the previous field X−1. When the currentlyreceived field is a first field of the video stream, the controller 16turns the processing performed by the motion adaptive converter 12 offbecause the motion adaptive converter 12 will not have sufficientinformation operate.

[0073] As discussed in the background of the invention section,interlaced scan data, whether frame or field based, alternates betweentop and bottom fields. However, in practice, the actually receivedinterlaced scan data may be missing a field such that two or more top ortwo or more bottom fields are received consecutively. When the currentfield is either preceded by or followed by a field of the same type(e.g., top or bottom), the controller 16 controls the multiplexer 14 tooutput the scanning line (i−1) from the first memory 2 as scanning line(i−1)′ of the generated progressive scan data PDATA, to next output theoutput from the interpolator 10 as scanning line (i)′ of the generatedprogressive scan data PDATA, and to subsequently output scanning line(i+1) from the first memory 2 as scanning line (i+1) of the generatedprogressive scan data PDATA. The generation of the i′th scanning line inthis manner will be referred to as the bob technique. Namely, in the bobtechnique, a frame of progressive scan data is produced from the currentfield and a field of complementary scan data generated by theinterpolator 10. Together the current field and the complementary fieldrepresent a frame of progressive scan data.

[0074] If the previous or next field is not missing and the video streamis frame based interlaced scan data, then the controller 16 controls themotion adaptive converter 12 to output the ith scanning line of the X−1field received from the second memory 4 and not perform motion adaptiveprocessing. The controller 16 also controls the multiplexer 14 to outputthe scanning line (i−1) from the first memory 2 as scanning line (i−1)′of the generated progressive scan data PDATA, to next output the ithscanning line from the X−1 field as scanning line (i)′ of the generatedprogressive scan data PDATA, and to subsequently output scanning line(i+1) from the first memory 2 as scanning line (i+1) of the generatedprogressive scan data PDATA. The generation of the i′th scanning line inthis manner will be referred to as the weave technique. In this example,it was assumed that the previous field X−1 was associated with the samepoint in time as the current field X−1. However, it may be the case thatthe next field X+1 is the field associated with the same point in timeas the current field. In this situation the next field would be selectedfor output. Namely, in the weave technique, two consecutive fields ofinterlaced scan data associated with the same point in time arealternately output on a scan line by scan line basis to produce a frameof progressive scan data.

[0075] If the previous or next field is not missing and the video streamis field based interlaced scan data, then the controller 16 controls themotion adaptive converter 12 to perform the motion adaptive processing.The controller 16 also controls the multiplexer 14 to output thescanning line (i−1) from the first memory 2 as scanning line (i−1)′ ofthe generated progressive scan data PDATA, to next output the outputfrom the motion adaptive converter 12 as scanning line (i)′ of thegenerated progressive scan data PDATA, and to subsequently outputscanning line (i+1) from the first memory 2 as scanning line (i+1) ofthe generated progressive scan data PDATA. The generation of the i′thscanning line in this manner will be referred to as the motion adaptivetechnique. Namely, in the motion adaptive technique, a frame ofprogressive scan data is produced from the current field and a field ofcomplementary scan data generated by the motion adaptive converter 12.Together the current field and the complementary field represent a frameof progressive scan data.

[0076] As will be appreciated from the disclosure, generating theprogressive scan data PDATA according to the weave technique produces afull frame of data substantially without motion artifacts when theinterlaced scan data IDATA is frame based. However, when the interlacedscan data IDATA is field based, the weave technique can result in anunacceptably deteriorated image when a substantial amount of imagemotion takes place over time. This is particularly noticeable when astill image is being displayed. By using the motion adaptive techniqueon field based interlaced scan data, a much improved image is obtained.Furthermore, when insufficient data is present to perform either theweave or motion adaptive techniques, a frame of progressive scan dataPDATA may still be created according to the bob technique.

[0077]FIG. 5 illustrates a second embodiment of the IPC 210 of FIG. 1.As shown, in this embodiment, the IPC 210 includes the same first,second and third memories 2, 4 and 6 storing the same scanning lines aswas described above with respect to the embodiment of FIG. 3. In thisembodiment, a controller 26 controls the operation of a spatialprocessor 20, a temporal processor 22 and a mode device 24 based on thesame video information received by the controller 16 in FIG. 3.

[0078] The spatial processor 20 receives the scanning lines from thefirst memory 2, and under the control of the controller 26 performsspatial interpolation thereon or directly outputs the scanning lines.When performing the spatial processing, the spatial processor 20performs either the interpolation performed by interpolator 10 orgenerates the spatially interpolated pixel value Ys generated asdescribed above with respect to the motion adaptive converter 12. Thespatial processing performed is controlled by the controller 26 asdescribed in detail below.

[0079] The temporal processor 22 receives the scanning lines from thefirst, second and third memories 2, 4 and 6. The temporal processor 22,under the control of the controller 26, either outputs the ith scanningline of the X−1 field received from the second memory 4 or outputs thetemporally interpolated pixel value Y_(T) generated as described abovewith respect to the motion adaptive converter 12.

[0080] The mode device 24 uses the outputs from the spatial processor 20and the temporal processor 22 to generate the progressive scan dataPDATA according to one of the bob, weave and motion adaptive techniques.The mode device 24, along with the spatial and temporal processors 20and 22 operate under the control of the controller 26 as discussed indetail below.

[0081] When the current field is preceded by or followed by a field ofthe same type, the controller 26 turns the temporal processor 22 off,and controls the mode device 24 to output the output received from thespatial interpolator 20. The controller 26 further controls the spatialprocessor 20 to output the scanning line (i−1) from the first memory 2as scanning line (i−1)′ of the generated progressive scan data PDATA, tonext output a scanning line generated by the same spatial interpolationperformed by the interpolator 10 as scanning line (i)′ of the generatedprogressive scan data PDATA, and to subsequently output scanning line(i+1) from the first memory 2 as scanning line (i+1) of the generatedprogressive scan data PDATA. Accordingly, a frame of progressive scandata is generated according to the bob technique.

[0082] If the previous or next field is not missing and the video streamis frame based interlaced scan data, then the controller 26 controls thespatial processor 20 to output the scanning lines received from thefirst memory 2, and controls the temporal processor 22 to output thescanning line (i) received from the second memory 4. The controller 26controls the mode device 24 to output the scanning line (i−1) of thefirst memory 2 as scanning line (i−1)′ of the generated progressive scandata PDATA, to next output scanning line (i) from the X−1 field asscanning line (i)′ of the generated progressive scan data PDATA, and tosubsequently output scanning line (i+1) of the first memory 2 asscanning line (i+1) of the generated progressive scan data PDATA.Accordingly, a frame of progressive scan data is generated according tothe weave technique.

[0083] If the previous or next field is not missing and the video streamis field based interlaced scan data, then the controller 26 controls thespatial processor 20 to output the scanning lines received from thefirst memory 2 and to generate the spatially interpolated pixel valueY_(S). The controller 26 also controls the temporal processor 22 togenerate temporally interpolated pixel value Y_(T). The controller 26controls the mode device 24 to combine the spatially interpolated pixelvalue Y_(S) and the temporally interpolated pixel value Y_(T) togenerate the spatio-temporal interpolated pixel value Y_(ST) in the samemanner as described above with respect to the motion adaptive converter12. The controller 26 further controls the mode device 24 to output thescanning line (i−1) from the first memory 2 as scanning line (i−1)′ ofthe generated progressive scan data PDATA, to next output thespatio-temporal interpolated pixel values Y_(ST) as scanning line (i)′of the generated progressive scan data PDATA, and to subsequently outputscanning line (i+1) from the first memory 2 as scanning line (i+1) ofthe generated progressive scan data. Accordingly, a frame of progressivescan data is generated according to the motion adaptive technique.

[0084] As discussed above, the embodiment of FIG. 5 generatesprogressive scan data PDATA according to the bob, weave and motionadaptive techniques to obtain the same benefits as described above withrespect to FIG. 3.

[0085] PIC of the Scanning Conversion Apparatus

[0086] Next, an example embodiment of the PIC 220 will be described withrespect to FIGS. 6 and 7. FIG. 6 illustrates an example embodiment ofthe PIC 220. In this embodiment, the PIC 220 includes a synchronoussignal generator 690 such as for a television. As shown, the synchronoussignal generator 690 generates a field identifier signal field_id, anodd horizontal sync signal odd h_sync and an even horizontal sync signaleven h_sync.

[0087] The field identifier indicates whether the current interlacedscan data field to generate from the generated progressive scan dataPDATA is an even field or an odd field. FIG. 7C illustrates an exampleof the field identifier signal. As shown, when the signal is high, anodd field is generated and when the signal is low an even field isgenerated. FIG. 7B illustrates the progressive horizontal synchronoussignal hsync(p). Each pulse of the progressive horizontal synchronoussignal hsync(p) represents one scanning line of pixel data. FIG. 7Aillustrates the progressive vertical synchronous signal vsync(p). Eachpulse represents the beginning of a new frame of progressive scan pixeldata. Accordingly, the number of progressive horizontal synchronoussignal hsync(p) pulses between consecutive progressive verticalsynchronous signal vsync(p) represents the number of scanning lines in aframe of the progressive scan data.

[0088]FIG. 7E illustrates an example of the odd horizontal sync signalodd_hsync and FIG. 7F illustrates an example of the even horizontal syncsignal even_hsync derived from the progressive horizontal synchronoussignal hsync(p). As shown, the odd and even horizontal sync signals havea frequency that is half the frequency of the progressive horizontalsynchronous signal hsync(p). Furthermore, the odd and even horizontalsync signals are shifted by one period of the progressive horizontalsync signal hsync(p) from one another. As shown, the odd horizontal syncsignal includes a pulse at the beginning of the odd field generationperiod, and the even horizontal sync signal includes a pulse at thebeginning of the even field generation period.

[0089] Before discussing the remainder of the PIC structure, horizontaland vertical blanking intervals for interlaced and progressive scan datawill be discussed. The scan of one horizontal line of interlaced dataoccurs at a frequency of 13.5 Mhz. During the scanning one line ofinterlaced scan data at this frequency 858 clock pulses of a video dataclock are generated. The first 138 clock pulses represent the horizontalblanking interval. This is the time it takes the scanner to move fromthe end of one scan line to the beginning of the next scan line. Thenext 720 clock pulses represent the pixels being scanned across the scanline. The progressive horizontal scanning frequency is twice that of theinterlaced horizontal scanning frequency, 27 Mhz. Accordingly, in thesame time, 2×858 progressive scan video clock pulses are generated. Thisequates to the scanning of two lines during the same time that one lineis scanned in interlaced horizontal line scanning.

[0090] Returning to FIG. 6, a reset multiplexer 610 selectively outputsone of the odd horizontal sync signal and the even horizontal syncsignal as a reset signal based on the field identifier field_id. Acounter 620 counts the pulses of a first clock signal generating clockpulses at the video data rate (e.g., 858 pulses per scan line) of theprogressive scan data until reset by the reset signal. As will beappreciated, the count values are associated with a period of theprogressive scan data.

[0091] The remainder of the description of the embodiments of thepresent invention are described for a video data rate of 858 clockpulses per scan line. However, one skilled in the art would understandthat the present invention is applicable to other rates. FIG. 7Dillustrates an example of the first clock signal. As will be appreciatedfrom FIG. 7D and the above description, during the odd field generationperiod indicated by the field identifier field_id, the counter 620 isonly reset by the pulses of the odd horizontal sync signal odd_hsync.Similarly, during the even field generation period indicated by thefield identifier field_id, the counter 620 is reset only by the pulsesof the even horizontal sync signal even_hsync. FIG. 7G illustrates thepulse count output by the counter 620 for a scan line during generationof an odd field. As will be appreciated from FIG. 7G and the abovedescription, the counter 620 generates count values at a progressivescanning frequency such that the count values are associated with aperiod of the progressive scan data. Namely, the counter 620 generatescount values associated with different periods of the progressive scandata based on whether the progressive scan data is being converted intoone of an odd and an even field of interlaced scan data. For example,the counter 620 generates count values associated with a odd scan lineand a subsequent even scan line of progressive data when the progressivescan data is being converted into an odd field of interlaced scan data,and the counter 620 generates count values associated with an even scanline and a subsequent odd scan line of progressive scan data when theprogressive scan data is being converted into an even field ofinterlaced scan data. In this manner, the counter 620 serves as a timerindicating a timing of two consecutive scan lines of the progressivescan data.

[0092] The pulse count generated by the counter 620 is received by asubtractor 6305, which generates a pixel count. The pixel count equalsthe pulse count minus 138 (i.e., the horizontal blanking interval).Accordingly, the pixel count represents when a scanning line is scanningthe pixels of a display in progressive scanning. FIG. 7H illustrates thepixel count output by the subtractor 6305. A second multiplexer 6307selectively outputs the pixel count and a zero value based on a controlsignal received from a first comparator 6301.

[0093] The first comparator 6301 determines if the pulse count isgreater than or equal to 138 and less than 859. Namely, the comparator6301 determines if the pulse count represents when a scanning line is tobe scanned. If so, the first comparator 6301 generates a control signal(e.g., a ‘1’) such that the second multiplexer 6307 outputs the pixelcount. If the pulse count is not greater than or equal to 138 nor lessthan 859, then the first comparator 6301 generates a control signal(e.g., ‘0’) such that the second multiplexer 6307 output the zero value.FIG. 7I illustrates the output of the second multiplexer 6307.

[0094] A first latch 6309 generates an write address (WA) based on thereceived output from the second multiplexer 6307. Specifically, thefirst latch 6309 stores the output of the second multiplexer 6307 inaccordance with the first clock signal. FIG. 7L illustrates the writeaddresses generated by the first latch 6309. As will be appreciated,when a scanning line of an odd field is being generated, write addressesare generated for the first of two consecutive scanning lines. Becausethe zero value is selected once the pulse count exceeds 858, the writeaddresses become zero for the next scanning line, at the end of whichthe pulse counter 620 is reset. The same operation takes place whengenerating scanning lines for an even field; however, because the pulsecounter 620 is reset by the even horizontal sync signal even_hsyncinstead of the odd horizontal synch signal odd_sync, the scanning linefor which write addresses are generated is shifted one scan line withrespect to the scanning line for which write addresses are generatedwhen generating write addresses for an odd field.

[0095] The pulse count output from the first counter 620 is alsoreceived by an arithmetic unit 6503. The arithmetic unit 6503 subtracts276 from the pulse count and divides the result by two to generate aninterlaced pixel count. The value 276 represents two horizontal blankingintervals (2*138=276) such that dividing the subtraction result producesa value representing a pixel count when scanning a line of interlaceddata. FIG. 7J illustrates the interlaced pixel count.

[0096] A third multiplexer 6505 selectively outputs the interlaced pixelcount and a zero value based on a control signal received from a secondcomparator 6501. The second comparator 6501 determines if the pulsecount is greater than or equal to 276. If so, the second comparator 6501generates a control signal (e.g., a ‘1’) such that third multiplexer6505 outputs the interlaced pixel count. If the pulse count is notgreater than or equal to 276, then the second comparator 6501 generatesa control signal (e.g., ‘0’) such that the third multiplexer 6501outputs the zero value. FIG. 7K illustrates the output of the thirdmultiplexer 6505.

[0097] A second latch 6507 generates read addresses (RAs) based on thereceived output from the third multiplexer 6505. Specifically, thesecond latch 6507 stores the output of the third multiplexer 6507 inaccordance with a second clock signal. The second clock signal has clockpulses at the video data rate of interlaced scan data. FIG. 7Millustrates the second clock signal. As shown, the frequency of thesecond clock signal is half that of the first clock signal illustratedin FIG. 7D. FIG. 7N illustrates the read addresses generated by thesecond latch 6507. As shown by FIG. 7N, even though the thirdmultiplexer 6507 may generate a stream of numbers such as 358, 358.5,359, 359.5, 360, etc., the second latch 6507 truncates the decimalportion of the interlaced pixel count. As a result, the second latch6507 generates the same read address for two consecutive counts of theprogressive pixel count and one count of the interlaced pixel count.Namely, the second latch 6507 generates read addresses at the interlacedvideo data rate.

[0098] A fourth multiplexer 6701 selectively outputs one of the writeaddress received from the first latch 6309 and the read address receivedfrom the second latch 6507 based on a write signal WR received from amemory 6703. FIG. 70 illustrates the write signal. As shown, the writesignal is a clock signal having the same frequency as the first clocksignal. When the write signal is high, the fourth multiplexer 6701outputs the write address, and the memory 6703 stores a pixel of theprogressive scan data. When the write address is low, the fourthmultiplexer 6701 outputs the read address, which will be the same fortwo consecutive pulses of the write signal WR, and the memory 6701outputs pixel data stored at the read address as the interlaced scandata IDATA′.

[0099] While the discussion above focused on the generation of a scanline for an odd field of interlaced scan data, the generation of a scanline for an even field of interlaced scan data will be readilyappreciated from the above description.

[0100] As shown above, the writing of progressive scan data into thememory 6703 and the reading of interlaced scan data out of the memory6703 are both based on the same signal, write signal WR. Furthermore,the generation of the write and read addresses is based on the first andsecond clocks which have a fixed relationship. As a result of the above,the generated interlaced scan data IDATA′ is synchronized with thegenerated progressive scan data PDATA.

[0101] Another example embodiment of the PIC 220 will be described withrespect to FIGS. 8 and 9. FIG. 8 illustrates an example embodiment ofthe PIC 220. The embodiment of FIG. 8 is the same as the embodiment ofFIG. 6, except for the differences discussed in detail below. Because,for the most part, the embodiment of FIG. 8 is the same as theembodiment of FIG. 6, only the difference will be discussed for the sakeof brevity.

[0102] In the embodiment of FIG. 8, the first counter 620 is reset basedon only one of the odd horizontal synchronous signal odd_hsync or theeven horizontal synchronous signal even_hsync. As a result, the timingfor resetting the pulse counter 620 depending on whether an even fieldor odd field is being generated does not take place. Instead, thisembodiment, provides a third subtractor 6303, a different firstcomparator 6301′ and a different second multiplexer 6307′ to effect thistiming change.

[0103] As shown, the third subtractor 6303 generates an even field scanline pixel count by subtracting the value 996 from the pulse count. Thevalue 996 equals 858 (the first scan line)+138 (the horizontal blankinginterval of the next scan line. As such, it will be appreciated that thefirst subtractor 6305 generates the odd field scan line pixel count.

[0104] The first comparator 6301′ determines whether an odd or top fieldis being generated and whether the pulse count represents the pixel datafor an odd scan line, and determines whether an even or bottom field isbeing generated and whether the pulse count represents the pixel datafor an even scan line. Specifically, the first comparator 6301′generates a control signal of “1” when the field identifier field_idindicates a top or odd field and the pulse count is greater than orequal to 138 and less than 859. The first comparator 6301′ generates acontrol signal of “2” when the field identifier field_id indicates eneven or bottom field and the pulse count is greater than or equal to996. When the pulse count is less than 138, the first comparator 6301′generates a control signal of “0”.

[0105] The first multiplexer 6307′ outputs the even scan line pixelcount when the first comparator 6301′ generates a control signal of “2”,outputs the odd scan line pixel count when the first comparator 6301′generates a control signal of “1”, and outputs the zero value when thefirst comparator 6301′ generates a control signal of ‘0’.

[0106]FIGS. 9A-9O illustrates the same waveforms as represented by FIGS.7A-7O, respectively. FIG. 8P illustrates the even field pixel countproduced by the third subtractor 6303.

[0107] As will be appreciated, this embodiment of the present inventionprovides the same synchronization between the generated progressive scandata PDATA and the generated interlaced scan data IDATA′ as discussed indetail above with respect to the embodiment of FIG. 6.

[0108] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications are intended to be included within the scope of theinvention.

1. A scanning conversion apparatus, comprising: a first converterconverting input interlaced scan data into progressive scan data; and asecond converter converting the progressive scan data output from thefirst converter to interlaced scan data.
 2. The apparatus of claim 1,wherein the first converter converts the input interlaced scan data intoprogressive scan data according to a technique selected from differenttechniques.
 3. The apparatus of claim 2, wherein the differenttechniques include, a spatial interpolation technique the involvesperforming spatial interpolation on a current field of the inputinterlaced scan data to produce a field of complementary scan data thattogether with the current field represents a frame of the progressivescan data; an alternative field output technique in which twoconsecutive fields of the input interlaced scan data are alternatelyoutput on a scan line by scan line basis to produce a frame of theprogressive scan data; and a spatial/temporal interpolation techniquethat involves performing directionally adaptive spatial interpolationadaptively combined with temporal interpolation using the current field,at least one previous field and at least one subsequent field of theinput interlaced scan data to produce a field of complementary scan datathat together with the current field represents a frame of progressivescan data.
 4. The apparatus of claim 1, wherein the second converterconverts the progressive scan data output from the first converter tointerlaced scan data such that the interlaced scan data output by thesecond converter is synchronized with the progressive scan data outputfrom the first converter.
 5. The apparatus of claim 1, wherein thesecond converter comprises: a counter generating count values at aprogressive scanning frequency such that the count values are associatedwith a period of the progressive scan data; a memory; a write addressgenerator generating write addresses for writing progressive scan datainto the memory based on output of the counter; and a generating readaddresses for outputting the progressive scan data written into thememory as interlaced scan data based on output of the counter.
 6. Theapparatus of claim 5, wherein the second converter further comprises: anaddress controller selectively applying the write and read addresses tothe memory from the write and read address generators.
 7. The apparatusof claim 6, wherein the address controller controls the application ofthe write and read addresses to the memory such that a scan line ofinterlaced scan data is read from the memory while progressive scan datafor the scan line is written to the memory.
 8. The apparatus of claim 5,wherein the counter generates count values associated with differentperiods of the progressive scan data based on whether the progressivescan data is being converted into one of an odd and an even field ofinterlaced scan data.
 9. The apparatus of claim 8, wherein the countergenerates count values associated with a odd scan line and a subsequenteven scan line of progressive data when the progressive scan data isbeing converted into an odd field of interlaced scan data, and thecounter generates count values associated with an even scan line and asubsequent odd scan line of progressive scan data when the progressivescan data is being converted into an even field of interlaced scan data.10. The apparatus of claim 5, wherein the counter generates count valuesassociated with two consecutive scan lines of progressive scan data. 11.The apparatus of claim 10, wherein the write address generator,comprises: a first write address generator generating first writeaddresses associated with a first of the two consecutive scan linesbased on the count values; a second write address generator generatingsecond write addresses associated with a second of the two consecutivescan lines based on the count values; and a write address controllerselectively outputting one of the first and second write addresses basedon whether the progressive scan data is being converted into one of anodd and even scan line of interlaced scan data.
 12. The apparatus ofclaim 11, wherein the write address controller receives a control signalindicating whether the progressive scan data is being converted into oneof an odd and even scan line of interlaced scan data.
 13. The apparatusof claim 10, wherein the read address generator converts the countvalues into read addresses associated with one scan line of interlacedscan data.
 14. The apparatus of claim 1, wherein the second converter,comprises: a memory; a timer indicating a timing of two consecutive scanlines of the progressive scan data; a write address generator receivinga control signal indicating which of the two consecutive scanning linesto write into the memory, and the write address generator generatingwrite addresses for the indicated scanning line based on the timingindicated by the timer; and a read address generator generating readaddresses to read the written line from the memory, the read addressgenerator beginning the generation of the read addresses based on thetiming indicated by the timer.
 15. A scanning conversion apparatus,comprising: an interlaced-to-progressive converter and aprogressive-to-interlaced converter connected in series to generateinterlaced scan data synchronized with progressive scan data output bythe interlaced-to-progressive converter.
 16. A progressive-to-interlacedscan data converter, comprising: a counter generating count values at aprogressive scanning frequency such that the count values are associatedwith a period of progressive scan data; a memory; a write addressgenerator generating write addresses for writing progressive scan datainto the memory based on output of the counter; and a read addressgenerator generating read addresses for outputting the progressive scandata written into the memory as interlaced scan data.
 17. The converterof claim 16, further comprising: an address controller selectivelyapplying the write and read addresses to the memory from the write andread address generators.
 18. The converter of claim 17, wherein theaddress controller controls the application of the write and readaddresses to the memory such that a scan line of interlaced scan data isread from the memory while progressive scan data for the scan line iswritten to the memory.
 19. The converter of claim 16, wherein thecounter generates count values associated with different periods of theprogressive scan data based on whether the progressive scan data isbeing converted into one of an odd and an even field of interlaced scandata.
 20. The converter of claim 19, wherein the counter generates countvalues associated with a odd scan line and a subsequent even scan lineof progressive data when the progressive scan data is being convertedinto an odd field of interlaced scan data, and the counter generatescount values associated with an even scan line and a subsequent odd scanline of progressive scan data when the progressive scan data is beingconverted into an even field of interlaced scan data.
 21. The converterof claim 16, wherein the counter generates count values associated withtwo consecutive scan lines of progressive scan data.
 22. The converterof claim 21, wherein the write address generator, comprises: a firstwrite address generator generating first write addresses associated witha first of the two consecutive scan lines based on the count values; asecond write address generator generating second write addressesassociated with a second of the two consecutive scan lines based on thecount values; and a write address controller selectively outputting oneof the first and second write addresses based on whether the progressivescan data is being converted into one of an odd and even scan line ofinterlaced scan data.
 23. The converter of claim 22, wherein the writeaddress controller receives a control signal indicating whether theprogressive scan data is being converted into one of an odd and evenscan line of interlaced scan data.
 24. The converter of claim 21,wherein the read address generator converts the count values into readaddresses associated with one scan line of interlaced scan data.
 25. Aprogressive-to-interlaced scan data converter, comprising: a memory; atimer indicating a timing of two consecutive scan line of progressivescan data; a write address generator receiving a control signalindicating which of the two consecutive scanning lines to write into thememory, and the write address generator generating write address for theindicated scanning line based on the timing indicated by the timer; anda read address generator generating read addresses to read the writtenline from the memory, the read address generator beginning thegeneration of the read addresses based on the timing indicated by thetimer.
 26. A method of scanning conversion, comprising: converting inputinterlaced scan data into progressive scan data; and converting theprogressive scan data into output interlaced scan data.
 27. The methodof claim 26, wherein the output interlaced scan data is synchronizedwith the progressive scan data.
 28. A method of converting progressivescan data to interlaced scan data converter, comprising: generatingcount values at a progressive scanning frequency such that the countvalues are associated with a period of progressive scan data; generatingwrite addresses for writing progressive scan data into the memory basedon output of the counter; generating read addresses for outputting theprogressive scan data written into the memory as interlaced scan data;storing progressive scan data in a memory based on the generated writeaddresses; and outputting interlaced scan data from the memory based onthe generated read addresses.